Ion channels

Ion channels are intrinsic proteins with a distinctive pore running through the middle. They are found in lipid bi layer membranes of cells and organelles. They allow the passage of ions in and out of cells and organelles via various modes of transport such as facilitated diffusion and active transport, and also allow a voltage gradient to be maintained. One way in which ion channels can be categorized is by their gating.

There are three types of ion gated channels:

1) Voltage-Gated ion channels

 e.g. Na⁺ and K⁺ channels found in nerve and muscle cells

2) Ligand Gated ion channels

 e.g. nAch receptor

3) Intracellular messenger-gated ion channels

By measuring the current of a single ion channel in a single cell we can learn three things: The conductance of the channel, the open state probability of the channel, and the selectivity of the channel (i.e. which ions move across the channel).